1. Field of the Invention
The present disclosure relates to a nozzle assembly of a vacuum cleaner, and more particularly, to a nozzle assembly of a vacuum cleaner capable of attenuating noise from a fan that drives a drum brush without compromising performance of the fan.
2. Description of the Related Art
Vacuum cleaners are among the most widely used home electronic appliances. Vacuum cleaners draw in air and dust from a surface being cleaned, using a suction force generated by a vacuum source.
Vacuum cleaners can clean a variety of places, including hard surfaces such as hard floors, and soft surfaces such as carpets or blankets. However, vacuum cleaners are not always convenient to use. Cleaning can be tiresome when cleaning fabrics such as carpets or blankets as the fabrics frequently stick to the vacuum cleaner.
Accordingly, conventional vacuum cleaners employ a drum brush inside a nozzle assembly and use a fan to drive the drum brush to prevent objects being cleaned from sticking to the nozzle assembly. This will be explained in greater detail below with reference to FIGS. 1 and 2.
FIG. 1 is a cross-section view of a conventional nozzle assembly having a drum brush and a fan, and FIG. 2 is a perspective view of a fan employed in the nozzle assembly of FIG. 1.
Referring to FIG. 1, a conventional nozzle assembly 1 includes a drum brush 4 and a fan 5 in an interior space defined between an upper casing 2 and a lower casing 3. The lower casing 3 includes a suction port 6 to draw in air and dust. Although not illustrated, the drum brush 4 and the fan 5 are connected by a belt. As the nozzle assembly 1 is pushed against a surface being cleaned and a vacuum cleaner is operated, air is drawn in through the suction port 6 of the lower casing 3, and the drawn-in air passes the fan 5. The fan 5 is made to rotate by the energy of air that passes therethrough. As the rotational force of the fan 5 is transmitted to the drum brush 4, the drum brush 4 rotates together with the fan 5. As the drum brush 4 rotates, drum bristles 4a formed on an outer circumference of the drum brush 4 hit the surface being cleaned, thereby preventing the surface being cleaned from sticking to the nozzle assembly 1, while particles on the surface are picked up.
A blocking plate 7 is disposed on the front of the fan 5 to increase the performance of the fan 5. The blocking plate 7 is generally formed as a rectangular plate. The blocking plate 7 reduces the area of the entrance to the fluid passage in the front of the fan 5, helping the fan 5 rotate at a high speed.
Referring to FIG. 2, the fan 5 includes a fan body 5a, a shaft member 5b extending from the center of the fan body 5a toward an axis of rotation, and a plurality of blades 5c arranged at regular intervals on a side of the fan body 5a. The plurality of blades 5c extend from the outer surface of the shaft member 5b and in a radial fashion on the fan body 5a. This type of fan, known as a centrifugal fan, in which the first ends of the blades 5c are integrally formed with the shaft member 5b, provides a relatively good fanning performance.
However, when implemented in a nozzle assembly 1 to drive the drum brush 4, the fan 5 causes a usually high-pitched agitating noise to be emitted from the nozzle assembly 1. This noise, which is called ‘blade passage frequency noise (BPF)’, is generated due to the blades 5c of the fast rotating fan 5 colliding with the air. A user may feel discomfort as the BPF noise increases.